This invention relates to water-jet-propelled recreational watercrafts which are small and light weight in relation to the size and weight of the typical operator.
This type of craft is generally used for recreational or leisure activities, and, because they are designed with the engine and other major parts contained in the front part of the craft and with a platform near the rear part of the craft for the operator, such manuevers as high-speed motion and sharp turns can only be performed while the operator is in the riding position and thus provides an overall balance of weight. In such a watercraft, the draft line differs dramatically when the operator is riding and the craft is in motion and when the craft is simply floating on the surface of the water.
Thus this type of craft is so designed as to be a system that is operated while the operator skillfully achieves a balance between himself and the craft.
Moreover, from a structural point of view of the craft itself, in order to both prevent the craft from sinking in the event that the operator falls off during operation and also to provide the craft with the ability to automatically reright itself after being capsized, various parts of the craft from the center to the stern area where the operator rides are filled with foam material to increase flotation. The craft's center of gravity (without an operator) is located toward the prow where the engine is located, and when there is no operator on the craft and it is simply floating on the surface of the water, the craft is trim with the prow at least partially submerged beneath the water surface. Thus, the draft line when the craft is simply floating on the surface of the water differs greatly from that during operation.
Therefore, with this type of watercraft, if the operator falls off into the water during operation, the craft immediately trims itself with the prow at least partially submerged beneath the surface of the water, thus creating a sudden increase in motion resistance; further, when the operator releases the controls, the craft continues its motion with the engine automatically maintained at idle setting. In this case, if the operator falls off the craft during operation, the craft will continue to move in an undetermined direction.
Thus, for this type of craft a mechanism has been proposed which, in the event that the operator falls off the craft, would automatically turn the steering nozzle of the craft's jet propulsion device in a fixed direction in order to cause the craft to automatically circle in the vicinity where the operator fell off, and thus facilitate recovery of the craft. Such an arrangement is described in Japanese Patent Pub. No. SHO. 54-30197.
However, when the aforementioned mechanism is used on such a craft, it has been found that, at the moment that the operator falls off the craft, the craft assumes a posture with its stern floating high in the water and the steering nozzle sprays the jet of water close to the surface of the water and in a particular direction. This situation thus limits the effectiveness of such a mechanism.
It is a general object of this invention to avoid the foregoing problems, by creating a difference, between the left and right sides of the craft, in the inherent motion resistance which occurs at the draft line, thus achieving a small watercraft with an extremely effective circling function without relying on a steering nozzle mechanism located at the stern of the craft.